# Reference

Here's the reference or code API, the classes, functions, parameters, attributes, and
all the FastAPI parts you can use in your applications.

If you want to **learn FastAPI** you are much better off reading the

### Is concurrency better than parallelism? { #is-concurrency-better-than-parallelism }

Nope! That's not the moral of the story.

Concurrency is different than parallelism. And it is better on **specific** scenarios that involve a lot of waiting. Because of that, it generally is a lot better than parallelism for web application development. But not for everything.

    id: what-did-you-do
    attributes:
      label: "What did you do?"
      description: "If possible, provide a recipe for reproducing the error. A complete runnable program is good. A link on [go.dev/play](https://go.dev/play) is better. A failing unit test is the best."
    validations:
      required: true
  - type: textarea
    id: actual-behavior
    attributes:
      label: "What did you see happen?"
    validations:
      required: true

          - translate-lang
          - update-outdated
          - add-missing
          - update-and-add
          - remove-all-removable
      language:
        description: Language to translate to as a letter code (e.g. "es" for Spanish)
        type: string
        required: false
        default: ""
      en_path:
        description: File path in English to translate (e.g. docs/en/docs/index.md)
        type: string

    // unless it's actually going to be used; validate() is called for all set method calls, so it
    // needs to be fast.
    // (We could instead generate the message once, when the set is created, but zero is better.)
    if (!validator.get()) {
      throw new IllegalStateException(errorMessage.get());
    }
  }

    withLock {
      while (headersQueue.isEmpty() && errorCode == null) {
        val doReadTimeout = callerIsIdle || doReadTimeout()
        if (doReadTimeout) {
          readTimeout.enter()
        }
        try {
          waitForIo()
        } finally {
          if (doReadTimeout) {
            readTimeout.exitAndThrowIfTimedOut()
          }
        }
      }

    @Inject
    private SessionScope sessionScope;

    protected String component() {
        return "installer";
    }

    @Test
    void testArtifactInstallation() throws Exception {
        sessionScope.enter();
        try {
            sessionScope.seed(MavenSession.class, mock(MavenSession.class));

            String artifactBasedir = new File(getBasedir(), "src/test/resources/artifact-install").getAbsolutePath();

    var $submitButton;
    if (e.which === 13) {
      $submitButton = $("input#submit, button#submit");
      if ($submitButton.length > 0) {
        $submitButton[0].submit();
      }
      // ignore enter key down
      return false;
    }
  });

  $(".table tr[data-href]").each(function() {
    $(this)
      .css("cursor", "pointer")
      .hover(
        function() {
          $(this).addClass("active");

I (the author, [@tiangolo](https://x.com/tiangolo)) will review it thoroughly and get back to you.

## Public Discussions

Please restrain from publicly discussing a potential security vulnerability. 🙊

It's better to discuss privately and try to find a solution first, to limit the potential impact as much as possible.

---

Thanks for your help!

    var $submitButton;
    if (e.which === 13) {
      $submitButton = $("input#submit, button#submit");
      if ($submitButton.length > 0) {
        $submitButton[0].submit();
      }
      // ignore enter key down
      return false;
    }
  });

  $(".table tr[data-href]").each(function() {
    $(this)
      .css("cursor", "pointer")
      .hover(
        function() {
          $(this).addClass("active");